Method and apparatus for continuous molding of fiber reinforced plastic member with curvature

ABSTRACT

In a continuous molding apparatus equipped with a long core  10  having a curvature disposed on a plane, a release film supplied from a lower release film feeder  20  is sent onto the core  10 , and prepreg sheets supplied from a prepreg sheet feeder  30  are laminated thereon and preformed. A release film supplied from a release film feeder  40  is disposed on top of the laminated body, before the body is sent into a hot press  50 . A puller  60  moves the laminated body without loading tension thereto. The laminated body enters a postcure device  70  in which thermosetting of the material is completed.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for continuouslymolding a member made of fiber reinforced plastics (FRP) having aconstant curvature, the FRP member having high strength and light weightsuitable for application to aircrafts or the like.

DESCRIPTION OF THE RELATED ART

Conventionally, it was common to use aluminum material as reinforcementframe in the body of a jumbo jet or other aircrafts, but recently,replacement of the aluminum frame with fiber reinforced plasticscontaining carbon or glass fiber is considered, in order to reduce theweight of the frame member. The FRP member used in an aircraft ismanufactured using a prepreg material in order to realize stablequality, and in general, after disposing a release film or othersecondary material on a mold, the necessary number of prepreg sheets aresequentially laminated thereon, which is then heated and pressed in anautoclave to form a member. The present inventors own a patent relatedto the continuous molding of an FRP member having a constant curvature,which is disclosed in Japanese Patent No. 3402481 (patent document 1).

One very important factor that affects the property of the moldedproduct formed by FRP is the orientation of the fibers containedtherein. When the orientation of fiber is slanted for over 5 degreeswith respect to the direction of tension, the strength of the member isdeteriorated, and the member cannot exert the predetermined strengthwhen load is placed thereon.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for continuousmolding that prevents tension from being loaded on the fiber during theprocesses, and prevents the orientational angle of fiber from varyinggreatly during curving of the prepreg that may cause deterioration ofstrength of the molded member.

The present invention is equipped with, as basic means, a core shaped tocorrespond to the shape of a molded member with a curvature and disposedon a plane, and comprises a step of feeding a release film deformed inadvance to correspond to the curvature of the molded member, a step offeeding multiple sheets of semi-cured prepregs formed by impregnatingcarbon fiber or glass fiber with thermosetting resin, a step oflaminating and deforming multiple layers of prepregs into a determinedshape, a step of hot pressing the laminated and deformed release filmand laminated member into a predetermined shape, and a step ofpostcuring the laminated member exiting the hot press, wherein pullersare disposed before and after the hot press to hold the laminated memberand to introduce the member to the hot press, so that no tension isplaced on the fiber of the prepreg while the hot pressing step is beingperformed.

According to the present invention, a fiber reinforced plastic memberwith a curvature is molded continuously while the meandering angle ofthe fiber in the prepreg is maintained small, so the present inventionenables to manufacture a structural member with high strength and lightweight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view of an FRP member;

FIG. 2 is an explanatory view showing the cross-sectional structure of amember;

FIG. 3 is an explanatory view showing the cross-sectional structure of amember;

FIG. 4 is a plan view showing the continuous molding apparatus of FRPmember;

FIG. 5 is a front view showing the continuous molding apparatus of FRPmember;

FIG. 6 show three side views of the prepreg sheet feeding/preformdevice;

FIG. 7 is a plan view showing the details of the prepreg sheetfeeding/preform device;

FIG. 8 is an explanatory view showing the gathering roller;

FIG. 9 is an explanatory view of the 45-degree bending roller and the90-degree bending roller;

FIG. 10 is an explanatory view of the hot press and pullers;

FIG. 11 is an explanatory view of the release film forming device;

FIG. 12 is an explanatory view of the mold for the release film formingdevice;

FIG. 13 is a time chart showing the operation of the continuous moldingapparatus; and

FIG. 14 is an explanatory view showing other examples of the productsformed according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A molded member formed of fiber reinforced plastics (FRP), the whole ofwhich being designated by reference number 1, is a beam-shaped membercomprising three surfaces 1 a, 1 b and 1 c with a channel-like crosssection.

A center line C₁ of the surface 1 a defining the bottom surface of achannel is curved in an arc having a radius R₁.

The radius of curvature R₁ is large, for example, around 15,000 mm.

The FRP molded member is formed by laminating multiple prepreg sheetsformed by impregnating reinforcing fiber such as carbon fiber or glassfiber with thermosetting plastic resin and semi-curing the same, andhot-pressing the laminated member to thereby continuously mold themember into a predetermined shape.

The molded member is then heated in a postcure device, so thatthermosetting is completed.

Reinforcing fiber has advantageous tensile strength. Therefore, aplurality of prepreg sheets having reinforcing fibers arranged along thelongitudinal direction of the member to be molded are laminatedappropriately with sheets formed by weaving the reinforcing fibers so asto achieve the required strength.

As shown in FIGS. 2 and 3, four unidirectional fiber sheets U₁, U₂, U₃,U₄ and three fabric sheets F₁, F₂, F₃ are laminated, and both sides ofthe laminated member are bent 90 degrees to form a channel member withthree surfaces 1 a, 1 b and 1 c.

FIG. 4 is a plan view of a continuous molding apparatus of an FRP memberaccording to the present invention, and FIG. 5 is a front elevationthereof.

A molding apparatus is for forming a channel member by continuouslysending release films and fiber reinforced prepreg sheets fed fromupstream toward the arrow A direction.

The molding apparatus comprises a core 10 having a cross sectional shapecorresponding to that of the molded member and having a curvaturecorresponding to the curvature of the member being formed, and disposedalong the core 10 are a lower release film supply device 20, a prepregsheet feeder/preform device 30, an upper release film feeder 40, a hotpress device 50, a puller 60 for pulling the molded member, and apostcure device 70.

The release films are disposed so as to sandwich the laminated body ofprepreg sheets impregnated with thermosetting resin before it enters thehot press device, so as to prevent the thermosetting resin leaking fromthe prepreg sheets from adhering to the mold. The release films areremoved from the molded member in the end.

The release films are curved in advance to correspond to the curvatureof the molded member by a release film molding device mentioned later.

The prepreg sheet feeder/preform device 30 peels off separate filmscovering and preventing the prepreg sheets impregnated with adhesiveagent from sticking to one another, and preforms the prepreg sheetsalong the core 10.

After disposing a release film fed from the upper release film supplydevice 40 on the upper surface of the material of the molded memberbeing preformed along the core 10, the preforming step is completed.

The preformed laminated body is heated and pressed in the hot pressdevice 50. If tension is placed on the laminated body during this step,the reinforcing fibers arranged within the laminated body with acurvature may be pulled and displaced from the line of curvature of themolded product.

Therefore, the molding apparatus of the present invention adopts amechanism for holding the laminated body at positions before and afterthe hot press 50 so as to move the laminated body in synchronism toprevent tension from being placed on the body.

FIG. 6 shows three views of a prepreg sheet feeder/preform device, andFIG. 7 is a plan view showing the details of the device.

The prepreg sheet feeder/preform device designated as a whole byreference number 30 comprises a base 300, a table 301 disposed on thebase, and a core 10 fixed above the table 301.

Above the base 300, four prepreg sheet feeders 311, 312, 313 and 314 aredisposed within a horizontal plane. Similarly, three prepreg sheetfeeders 315, 316 and 317 are disposed within a vertical plane.

Four prepreg sheet feeders 311, 312, 313 and 314 disposed within ahorizontal plane are for supplying to a laminated body prepreg sheetsU₁, U₂, U₃ and U₄ having reinforcing fibers arranged in unidirectionalfashion, as explained with reference to FIG. 3.

The three prepreg sheet feeders 315, 316 and 317 disposed within avertical plane are for supplying fabric prepreg sheets F₁, F₂ and F₃.

The prepreg sheets are tacky under room temperature. Therefore, thinplastic films called separate films are disposed on the front and backsurfaces of each sheet in order to prevent the sheets from sticking whenformed into a roll for feeding. When in use, the separate films arepeeled off allowing the sheets to be laminated.

In FIG. 7, the prepreg sheet feeder 311 is equipped with a roll ofprepreg sheet U₁, containing reinforcing fibers arrangedunidirectionally (in the longitudinal direction), the roll havingseparate films S₁ and S₂ adhered to both sides of the prepreg sheetbefore it is formed into a roll.

Along with the feeding of the prepreg sheet U₁, the separate films S₁and S₂ are reeled into rollers 311 a and 311 b, respectively.

The six other prepreg sheet feeders 312, 313, 314, 315, 316 and 317 areequipped with similar separate film reels, the detailed explanation ofwhich is omitted.

The prepreg sheet feeder/preform device 30 comprises three sets ofgathering rollers 350, 45-degree bending rollers 320, and 90-degreebending rollers 330.

FIG. 8 is an explanatory view showing the structure of the gatheringroller 350.

The prepreg sheet laminated body P fed from the prepreg sheet feeder 351is sandwiched between a pair of feed rollers 352 and transmitted in thearrow A direction.

The feed rollers 352 are driven via a servomotor, and the feedingquantity is controlled thereby.

The prepreg sheet laminated body P is sandwiched between an upper mold355 and a lower mold 356, by which a gather (crease) G is providedthereto.

The carbon fiber contained in the prepreg sheet laminated body P is notstretchable, but by creasing the body, it can be shrunk in thelongitudinal direction.

Therefore, by providing a gather G deeper on one side P₂ than on theother side P₁ of the prepreg sheet body P, the prepreg sheet body P canbe bent to have a radius of curvature R₁ with respect to a plane.

FIG. 9 is an explanatory view showing the structure of the 45-degreebending roller 320 and 90-degree bending roller 330.

The 45-degree bending roller 320 comprises a frame 321 disposed abovethe core 10, a press roller 322 fixed to the frame 321 for pressing thelaminated body P located on the upper surface of the core 10, and a bendroller 324 for bending both sides of the laminated body P for 45 degreesalong the core 10. The pressing force of the press roller 322 can becontrolled via a pressurizing spring 323.

The laminated body having passed through the 45-degree bending roller320 and having both ends bent by 45 degrees enters the 90-degree bendingroller 330.

The 90-degree bending roller 330 comprises a frame 331, a press roller332 fixed to the frame 331 for pressing the laminated body P located onthe upper surface of the core 10, and a bend roller 324 for bending bothsides of the laminated body P for 90 degrees along the core 10.

The pressing force of the press roller 332 can be controlled via apressurizing spring 323, and the pressing force of the bend roller 324can be adjusted via a pressurizing spring 325.

FIG. 10 is an explanatory view showing the structure of the hot pressdevice 50 and the pullers 60, 60 for the laminated body.

The hot press device 50 comprises a hot press unit 502 equipped above aframe 501. Inside the hot press unit 502 are equipped molds for heatingand pressing the laminated body P transmitted along the core 10, and themolds are pressed by piston cylinder units 510, 520 and 530,respectively.

When a predetermined hot press treatment is completed, the laminatedbody P on the core 10 is transferred for a predetermined distance.

The pullers 60 are disposed before and after the hot press device 50 soas to pull the laminated body P.

The pullers 60 comprise gripping devices 610, 620, 630 and 640 that moveback and forth along the arrow A direction on the table 601.

The two gripping devices 610 and 620 disposed on the upstream side ofthe hot press device 50 each comprise a cylinder unit 612 or 622, andhold the laminated body P.

Similarly, the two gripping devices 630 and 640 disposed on thedownstream side of the hot press device 50 each comprise a cylinder unit632 or 642, and hold the laminated body P.

The upstream gripping devices 610, 620 and the downstream grippingdevices 630, 640 are connected via a rod 650, by which the devices movein the arrow A direction in synchronism.

By this movement, the laminated body P within the hot press device 50 ispulled for a predetermined length.

A sensor 670 is disposed on the entrance side of the hot press device 50for accurately measuring the distance of movement of the laminated bodyP.

According to this distance of movement of the laminated body P, accuratelengths of release films and prepreg sheets are supplied.

According to the above-explained construction, the laminated body Ppassing through the hot press device is heated and pressed with notension added thereto.

Thus, thermosetting of the laminated body with a curvature can beperformed without disarranging the alignment of the reinforcing fiber.Thus, the strength of the reinforcing fiber is maintained by thecompleted product.

After exiting the hot press device 50, the laminated body P is sent intoa postcure device 70, where thermosetting of the laminated body iscompleted in a furnace.

FIG. 11 is an explanatory view showing the forming device of the releasefilm, and FIG. 12 is an explanatory view showing the forming mold of therelease film.

Since the molding apparatus according to the present invention isdesigned to manufacture a member having a curvature, it is preferablethat the release films disposed on the top and bottom surfaces of theprepreg sheet is curved along the core.

Therefore, the present invention comprises a device for preforming therelease film in advance.

The forming device of the release film designated as a whole byreference number 80 comprises a frame 800, and a feeding reel 810 and awinding reel 820 of a release film S₁ disposed on the frame. The feedingreel 810 comprises a brake 812 for placing appropriate tension on therelease film S₁. The winding reel 820 comprises a motor 822 for windingin the release film S₁.

The release film S₁ provided from the feeding reel 810 passes through afilm bending mold device 830. Rollers 830 a and 830 b for pulling downthe film are disposed before and after the mold device 830.

FIG. 12 is an explanatory view showing the structure of the mold 832equipped within the mold device 830. The mold 832 comprises a firstplanar surface 832 a and a second planar surface 832 c, and the planarsurfaces are connected via an inclined surface 832 b. The first planarsurface 832 a is located at a lower position than the second planarsurface 832 c.

The release film is transmitted on the mold 832 in the direction ofarrow E. Since the release film is pulled down by rollers 830 a and 830b disposed in front of and behind the mold, the release film passing theside of the upper planar surface 832 c is drawn more. Thus, the formedrelease film S₁ has a curvature within a plane.

The release film S₁ having passed through the mold device 830 enters acreasing roller 840, where creases corresponding to the shape of themember are formed to the film in the longitudinal direction.

The release film S₁ passes through a film holding unit 850 and a guideroller 860.

The release film S₁ is thus preformed, so a member having a curvaturewithin a plane can be formed efficiently.

FIG. 13 is a time chart showing the operations of the motor for sendingout the prepreg sheet, the pullers and the hot press.

FIG. 14 is an explanatory view showing other examples of thecross-sectional shapes of the fiber reinforced plastic members having acurvature formed by the molding apparatus of the present invention

Product Wa has an L-shaped cross section, and Wb has an H-shaped crosssection. Product Wc has a Z-shaped cross section, and Wd has ahat-shaped cross section.

As explained, the present invention enables to form a fiber reinforcedprepreg material into a member having a curvature, which can be appliedto forming a structural member of an aircraft required to be both strongand light weight.

1. A method for continuously molding a fiber reinforced plastic memberwith a curvature utilizing a core having a shape corresponding to theshape of the member with a curvature and disposed on a plane, the methodcomprising: a step of feeding a release film deformed in advance tocorrespond to the curvature of the molded member; a step of feedingplural sheets of semi-cured prepreg material formed by impregnatingcarbon fiber or glass fiber with thermosetting resin; a step oflaminating and deforming the prepreg into a predetermined shape; a stepof hot-pressing the laminated and deformed release film and laminatedbody into a predetermined shape; and a step of post-curing the laminatedbody exiting the hot-pressing step by heating the same; wherein thehot-pressing step is performed while pullers disposed before and afterthe hot-pressing step for gripping the laminated body and introducingthe same into the hot press is used to prevent tension from being placedon the fiber in the prepreg.
 2. The method for continuously molding afiber reinforced plastic member with a curvature according to claim 1,wherein during the step of deforming the prepreg into a shape with acurvature, the width of the prepreg is adjusted so that the angle ofmeandering of the fiber in the longitudinal direction is 5 degrees orsmaller.
 3. A continuous molding apparatus for molding a fiberreinforced plastic member with a curvature utilizing a core having ashape corresponding to the shape of the member with a curvature anddisposed on a plane, the apparatus comprising: a device for feeding arelease film deformed in advance to correspond to the curvature of themolded member; a device for feeding plural sheets of semi-cured prepregmaterial formed by impregnating carbon fiber or glass fiber withthermosetting resin; a device for laminating and deforming the prepreginto a predetermined shape; a hot press device for heating and pressingthe laminated and deformed release film and laminated body into apredetermined shape; a puller disposed before and after the hot pressdevice for gripping the laminated body and introducing the same into thehot press device; and a postcure device for heating the laminated bodyexiting the hot press device; wherein the hot press is performed whilepreventing tension from being placed on the fiber in the prepreg.
 4. Theapparatus for continuously molding a fiber reinforced plastic memberwith a curvature according to claim 3, wherein the device for feedingthe prepreg comprises a mechanism for reeling out a specific amount ofprepreg by sensing the amount of movement of the laminated body.
 5. Theapparatus for continuously molding a fiber reinforced plastic memberwith a curvature according to claim 3, wherein the puller for grippingthe laminated body and introducing the same into the hot press device isinterlocked with the hot press device, so that the puller moves thelaminated body for a specific amount of distance when a mold of the hotpress device is opened.